This invention relates to a method and apparatus for the control of the air-fuel ratio of a mixture to an internal combustion engine.
The air-fuel ratio to an internal combustion engine has been controlled by calculating a value of fuel-delivery requirement for the engine as a function of engine load and modifying the calculated fuel-delivery requirement value based upon various correction factors determined from engine operating parameters including battery voltage, cylinder-head coolant-temperature, engine speed, etc. Such conventional air-fuel ratio control is satsifactory as long as the air-fuel ratio to the engine is adjusted at the stoichiometric value, but it has been found that a limitation is encountered in attempting to improve fuel economy since the air-fuel ratio cannot be controlled at a desired lean value without deteriorating engine operation stability.
Therefore, the present invention provides a method and apparatus for controlling the air-fuel ratio to an engine which can improve fuel economy to a considerable extent without deteriorating engine operation stability.